Pyrolysis of beta-oximino-tert.-butyl pyridinium chloride



Patented May 31, 1949 1 i UNITED STATES BATE-NT, OFFICE Charles B. Wooster, Philadelphia,-'Pa., assign'or t'o Rohm & Haas Company, Philadelphia, Pa., a corporation of Delaware No Drawing. Application December 18, 1947, Serial No. 792,593

1 Claim. (Cl. 260-4653) 1 This invention deals with a method for preparether, and chloroform. It melts with decomposiing methacrylonitrile. The process involves maktion at 180-182 C. ing a quaternary ammonium salt by the reaction When the pyridinium chloride is heated at of pyridine and the dimer formed by the additemperatures from about 175 C. to 250 C., de-

tion of equimolecular proportions of nitrosyl chlo- 5 composition occurs. Slow decomposition may beride and isobutene and pyrolysing the quaternary gin below 175 C., .particularly in the case of imammonium salt. From the pyrolysis products pure salt. Decomposition proceeds smoothly at there are obtainable methacrylonitrile, frequent- 180 C. to 200 C.

ly with varying proportions of methacrolein A batch f 100 parts by eight of b t -oxioxime, which latter, if desire m y be dehydrated in mino-tert.-buty1 pyridinium chloride was placed to methacrylonitrile in a subsequent operation. in a distilling flask in an oil bath. Evidence of Otherwise, the two products, when obtained todecomposition was noted when the bath was gether, may be separated and used as such for heated to 175 C. The temperature of the bath any of their various applications. was raised to 190 C. A colorless liquid slowly The dimeric addition product is formed by redistilled from the flask and was condensed. This acting nitrosyl chloride and isobutene, 2-methyl liquid was fractionated into three parts. The propene, at temperatures of about 30 C. down to first, dried over sodium sulfate, was obtained 15 C. or even lower. The addition reaction mainly at 90 C. and consisted of methacrylonimay be eifected directly or in solvent, light cuts trile. A small intermediate fraction was then of petroleum, chloroform, chlorobenzene, and the taken oil between 90 C. and 125 C. It separated like being suitable solvents. A white solid is into an aqueous and non-aqueous layer, from formed along with some blue liquid. The solid is which additional products were recoverable. The readily separable and may be rinsed free of any third fraction was taken oiT above 125 C. with blue liquid adhering to it by means of petroleum most of the material distilling at 145 C. This ether or other volatile solvent. The solid then fraction was practically pure methacrolein corresponds by analysis to the dimeric addition oxime.

product of equimolecular proportions of nitrosyl The residue from the pyrolysis was found to be chloride and isobutene. pyridine hydrochloride, melting at 82 C.

A monomeric quaternary ammonium salt is In another procedure for making pyridinium formed by mixing and reacting the dimeric adchloride there were taken 238 grams of pyridine dition product and pyridine. The composition of which was mixed with 700 ml. of benzene in a this salt corresponds to that of beta-oximinotwo-liter, three-necked flask equipped with metert.-butyl-pyridinium chloride, chanical stirrer, reflux condenser, and funnel for crime CH-NOH the adding of material. The mixture was warmed 5 to 50 C. and 243 grams of the dimeric addition CBHENCI product from isobutene and nitrosyl chloride To complete the reaction the mixture may be added in successive portions during the course of heated up to 115 C. The quaternary salt sepaan hour. External cooling was used to prevent rates as awhite solidthe temperature rising much above 50 C. The

Thus, 30 parts by Weight of th d i addi- 0 reaction mixture was then stirred for an hour tion product was added t 00 parts of pyridine while the temperature thereof was held at 50 C. The mixture was stirred and heated at 50 C. A The p r dinium salt crystallized out and was white solid was precipitated. It was separated, p ted y filtration. The weight of the dried washed with petroleum ether, and dried. The l W s 3 7 grams, corresponding to a yield of yield was 47 parts. Analysis of this product gave .5%-

a nitrogen content of 13.97% and a chlorine con- A portion of 50 grams of the above-prepared tent of 17.71%. The corresponding theoretical beta-oximino-tert-buwl pyridinium chloride was values are 13.90% and 17.59%, respectively. This placed in a glass flask fitted with stirrer, still new salt is soluble in water, methanol, and anihead, and tunnel for adding this pyridinium chloline, but insoluble in pyridine, ether, petroleum ride. The flask was then heated to C.

Vapors passed from the still head into a condenser, the gases therefrom were passed through a trap chilled with dry ice. During the course of an hour 250 grams of additional beta-oximinotert.-buty1 pyridinium chloride was added in small increments. The temperature was gradually increased to 220 C. From the liquid collected water was separated and the organic layer was fractionated. There was thus obtained a yield of 59.4% of methacrylonitrile.

Iclaim:

A process for preparing methacrylonitrile which comprises reacting at 50 C. pyridine and the dimer formed by the addition of equimolecular proportions of nitrosyl chloride and isobutene, thereby forming beta-oXimino-tert.-butyl pyridinium chloride, separating said pyridinium chloride, heating it at 175 C. to 250 0., thereby forming methacrylonitrile, and separating methacrylonitrile from the heated pyridinium chloride.

CHARLES B. WOOSTER.

REFERENCES CITED UNITED STATES PATENTS 10 Number Name Date Lazier et al Mar. 11, 1941 Lichty Sept. '7, 1943 Kung May 1, 1945 Spence Sept. 25, 1945 Crowder et a1. Feb. 5, 1946 Dutcher July 16, 1946 Tuerck et a1 Mar. 4, 1947 

